Coating Device, Coating Method, Method of Manufacturing Positive Electrode, and Method of Manufacturing Solid-State Battery

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2024-057704, filed on 29 Mar. 2024, the content of which is incorporated herein by reference.

The present invention relates to a coating device, a coating method, a method of manufacturing a positive electrode, and a method of manufacturing a solid-state battery.

In recent years, research and development pertaining to batteries that contribute to improving energy efficiency has been carried out in order to be able to ensure many people have access to sustainable, advanced energy that is affordable and reliable.

A battery includes a positive electrode having a positive electrode current collector and a positive electrode mixture layer, a negative electrode having a negative electrode current collector and a negative electrode mixture layer, and an electrolyte, and a coating device is used when the battery is manufactured.

Patent Document 1 describes a coating device that applies a slurry to a surface of a continuously moving sheet-shaped member. Here, the coating device includes a die head that includes a slit-shaped discharge port facing a backup roll that supports the sheet-shaped member. The coating device further includes a first gas nozzle that is disposed on a lateral side of the sheet-shaped member at a position immediately beyond the discharge port, and oriented so as to supply pressurized gas, in a direction along the width direction, to a width end edge of a slurry layer applied to the sheet-shaped member. In addition, the coating device includes a second gas nozzle that is disposed downstream of the first gas nozzle and above the backup roll to face the width ends of the slurry layer, and oriented so as to supply pressurized gas in a direction perpendicular to the surface of the slurry layer.

However, in the coating device described in Patent Document 1, when the slurry is intermittently discharged from the die head, dragging occurs at the terminal end of the discharged slurry.

An object of the present invention is to provide a coating device and a coating method capable of preventing dragging at a terminal end of a discharged slurry even if the slurry is intermittently discharged from a die head.

According to the present invention, it is possible to provide a coating device and a coating method capable of preventing dragging at a terminal end of a discharged slurry even if the slurry is intermittently discharged from a die head.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

As shown in, a coating deviceincludes: a conveyance rollerthat is a conveyer for continuously conveying a sheet-shaped material-to-be-coated M; and a first die headthat intermittently discharges a first slurry Ltoward a first surface region Sof the material-to-be-coated M being continuously conveyed, to discontinuously form a first coated section C(see). The coating devicefurther includes a first air nozzlethat is a first gas ejector for ejecting a first gas Atoward the terminal end of the intermittently discharged first slurry L. This prevents dragging at the terminal end of the first slurry Ldischarged from the first die head, resulting in an improved shape accuracy of the first coated section C. Here, the first die headdischarges the first slurry Lin a direction substantially perpendicular to the convey direction Dof the material-to-be-coated M in the first surface region S. The first air nozzleejects the first gas Ain a direction substantially parallel to the convey direction Dof the material-to-be-coated M in the first surface region S.

In order to eject the first gas Atoward the terminal end of the intermittently discharged first slurry L, the timing of ejecting the first gas Ajust needs to be adjusted based on the coating speed of the first slurry L(the conveying speed of the material-to-be-coated M), the flow rate of the first gas A, and the timing of stopping the discharge of the first slurry L.

At this time, the coating speed of the first slurry L(the conveying speed of the material-to-be-coated M) is not particularly limited, but is, for example, 10 m/min to 60 m/min. In addition, the ejection pressure of the first gas Ais not particularly limited, but is, for example, 10 kPa to 700 kPa. Furthermore, the viscosity of the first slurry Lat 25° C. is not particularly limited, but is, for example, 1000 mPa·s to 3000 mPa·s.

If the first gas Ais not ejected toward the terminal end of the intermittently discharged first slurry L, dragging will occur at the terminal end of the first slurry Ldischarged from the first die head(see).

The first die headdischarges the first slurry Land has a slit-shaped first discharge portextending in the width direction W of the conveyance roller(material-to-be-coated M). The first air nozzleejects the first gas Aand has a slit-shaped first ejection portextending in the width direction W of the conveyance roller(see). This further improves the shape accuracy of the first coated section C. At this time, the first ejection portis disposed in the vicinity of the first discharge port. The width of the first ejection portis not particularly limited, but is, for example, 500 mm to 700 mm.

As shown in, the first air nozzlehas a first main bodyand a second main bodythat extend in the width direction W of the conveyance roller. The first ejection portis formed between the first main bodyand the second main body. At this time, the first main bodyis disposed close to the first die headand the second main bodyis disposed close to the conveyance roller(material-to-be-coated M), and the first main bodyextends closer to the first die headthan the second main bodydoes (see). As a result, the first air nozzlecan be brought closer to the first discharge portof the first die headto efficiently eject the first gas A.

Furthermore, since the first main bodyextends closer to the first die headthan the second main bodydoes, the first gas Ais guided toward the terminal end of the intermittently discharged first slurry L, and the first air nozzledoes not interfere with the conveyance roller.

The first air nozzlefurther has: a plurality of first supply portsthrough which the first gas Ais supplied from a supply source (e.g., a tank) of the first gas A; and a first gas junctionthat is connected to the plurality of first supply portsand the first ejection port, and that merges the first gas Asupplied from the plurality of first supply ports. At this time, the plurality of first supply portsare formed in the width direction W (depth direction in the figure) of the conveyance roller.

The first supply portsand the first gas junctionhave a dimension in the thickness direction larger than the first ejection port. The first gas junctionhas an inclined surface Ithat is inclined toward the first ejection port. In other words, the first main bodyis formed with a groove-shaped section Gextending in the width direction W of the conveyance roller, the second main bodyis a plate-shaped member, and the first gas junctionis formed between the first main bodyand the second main body. At this time, the inclination angle of the inclined surface Iis not particularly limited, but is, for example, 10° or more and 80° or less.

The first die headis not particularly limited as long it is capable of intermittently discharging the first slurry Lto discontinuously form the first coated section C, and any known die head can be used.

As shown in, the coating devicefurther includes a second die head. The second die headintermittently discharges the second slurry Ltoward the second surface region Sof the material-to-be-coated M being continuously conveyed, to discontinuously form the second coated section C(see). At this time, the second surface region Sis located downstream of the first surface region S, and the second coated section Cis formed in a region where the first coated section Cis not formed. As a result, since the shape accuracy of the first coated section Cis high, the shape accuracy of the second coated section Cis also high. Here, the second die headdischarges the second slurry Lin a direction substantially perpendicular to the convey direction Dof the material-to-be-coated M in the second surface region S.

The coating devicefurther includes a second air nozzlethat is a second gas ejector for ejecting the second gas Atoward the terminal end of the intermittently discharged second slurry L. This prevents dragging at the terminal end of the second slurry Ldischarged from the second die head, resulting in an improved shape accuracy of the second coated section C. Here, the second air nozzleejects the second gas Ain a direction substantially parallel to the convey direction Dof the material-to-be-coated M in the second surface region S.

In order to eject the second gas Atoward the terminal end of the intermittently discharged second slurry L, the timing of ejecting the second gas Ajust needs to be adjusted based on the coating speed of the second slurry L(the conveying speed of the material-to-be-coated M), the flow rate of the second gas A, and the timing of stopping the discharge of the second slurry L.

At this time, the coating speed of the second slurry L(the conveying speed of the material-to-be-coated M) is not particularly limited, but is, for example, 10 m/min or more and 60 m/min or less. The ejection pressure of the second gas Ais not particularly limited, but is, for example, 10 kPa or more and 700 kPa or less. The viscosity of the second slurry Lat 25° C. is not particularly limited, but is, for example, 1000 mPa·s or more and 3000 mPa·s or less.

Similarly to the first die head, the second die headdischarges the second slurry Land has a slit-shaped second discharge portextending in the width direction W of the conveyance roller. Similarly to the first air nozzle, the second air nozzleejects the second gas Aand has a slit-shaped second ejection portextending in the width direction W of the material-to-be-coated M. This further improves the shape accuracy of the second coated section C. At this time, the second ejection portis disposed in the vicinity of the second discharge port

As shown in, the second air nozzlehas a third main bodyand a fourth main bodythat extend in the width direction W of the conveyance roller. The second ejection portis formed between the third main bodyand the fourth main body. At this time, the third main bodyis disposed close to the second die headand the fourth main bodyis disposed close to the conveyance roller(material-to-be-coated M), and the third main bodyextends closer to the second die headthan the fourth main bodydoes (see). As a result, the second air nozzlecan be brought closer to the second discharge portof the first die headto efficiently eject the second gas A. Furthermore, since the third main bodyextends closer to the second die headthan the fourth main bodydoes, the second gas Ais guided toward the terminal end of the intermittently discharged second slurry L, and the second air nozzledoes not interfere with the conveyance roller.

The second air nozzlefurther has: a plurality of second supply portsthrough which the second gas Ais supplied from a supply source (e.g., a tank) of the second gas A; and a second gas junctionthat is connected to the plurality of second supply portsand the second ejection port, and that merges the second gas Asupplied from the plurality of second supply ports. At this time, the plurality of second supply portsare formed in the width direction W (depth direction in the figure) of the conveyance roller.

The second supply portsand the second gas junctionhave a dimension in the thickness direction larger than the second ejection port. The second gas junctionhas an inclined surfacethat inclines toward the second ejection port. In other words, the third main bodyis formed with a groove-shaped section Gextending in the width direction W of the conveyance roller, the fourth main bodyis a plate-shaped member, and the second gas junctionis formed between the third main bodyand the fourth main body. At this time, the inclination angle of the inclined surface Iis not particularly limited, but is, for example, 10° or more and 80° or less.

The second die headis not particularly limited as long it is capable of intermittently discharging the second slurry Lto discontinuously form the second coated section C, and any known die head can be used.

Note that, as needed, the second air nozzlemay be omitted, and the second die headmay further be omitted.

A coating method of this embodiment includes a step of continuously conveying the sheet-shaped material-to-be-coated M while intermittently discharging a first slurry Lfrom a first die headtoward a first surface region Sof the material-to-be-coated M being continuously conveyed, to discontinuously form a first coated section C. The coating method can be implemented using the coating device. At this time, a first gas Ais ejected toward the terminal end of the intermittently discharged first slurry L. This prevents dragging at the terminal end of the first slurry Ldischarged from the first die head, resulting in an improved shape accuracy of the first coated section C. In addition, the first slurry Lis discharged in a direction substantially perpendicular to the convey direction Dof the material-to-be-coated M in the first surface region S, and the first gas Ais ejected in a direction substantially parallel to the convey direction Dof the material-to-be-coated M in the first surface region S.

The coating method of this embodiment may further include a step of intermittently discharging the second slurry Lfrom the second die headtoward the second surface region Sof the material-to-be-coated M being continuously conveyed, to discontinuously form the second coated section C. At this time, the second surface region Sis located downstream of the first surface region S, and the second coated section Cis formed in a region where the first coated section Cis not formed. As a result, since the shape accuracy of the first coated section Cis high, the shape accuracy of the second coated section Cis also high. Here, the second slurry Lis discharged in a direction substantially perpendicular to the convey direction Dof the material-to-be-coated M in the second surface region S.

The coating method of this embodiment may eject the second gas Atoward the terminal end of the intermittently discharged second slurry L. At this time, the second gas Ais ejected in a direction substantially parallel to the convey direction Dof the material-to-be-coated M in the second surface region S. This prevents dragging at the terminal end of the second slurry Ldischarged from the second die head, resulting in an improved shape accuracy of the second coated section C. Here, the second gas Ais ejected in a direction substantially parallel to the convey direction Dof the material-to-be-coated M in the second surface region S.

The coating method of this embodiment may further include a step of heating and drying the material-to-be-coated M on which the first coated section C(and the second coated section C) has (have) been formed.

The coating method of this embodiment may be applied, for example, to the manufacture of positive electrodes, negative electrodes, and solid electrolyte layers that constitute batteries.

A method of manufacturing a positive electrode of this embodiment is a method of manufacturing a positive electrode through the coating method of this embodiment. Here, the material-to-be-coated M is a positive electrode current collector, the first slurry is a slurry for a positive electrode mixture layer, and the second slurry is a slurry for an insulating layer. This provides a positive electrode having high shape accuracy of the positive electrode mixture layer and the insulating layer.

The positive electrode current collector is not particularly limited, but may be, for example, aluminum foil.

The slurry for a positive electrode mixture layer includes, for example, a positive electrode active material.

The positive electrode active material is not particularly limited, but may be, for example, lithium iron phosphate.

The slurry for an insulating layer includes an insulating material. The insulating material is not particularly limited, but may be, for example, alumina.

The method of manufacturing a positive electrode of this embodiment may further include a step of continuously forming a second insulating layer on both sides of the positive electrode mixture layer in the width direction W. At this time, the second insulating layer may also be formed when the positive electrode mixture layer is formed.

A method of manufacturing a solid-state battery of this embodiment includes a step of obtaining a positive electrode through the method of manufacturing a positive electrode of this embodiment. This prevents short circuits in the solid-state battery.

The method of manufacturing a solid-state battery of this embodiment may further include a step of forming a solid electrolyte layer on the positive electrode mixture layer to form a positive electrode-solid electrolyte layer laminate.

The solid-state battery is not particularly limited, but may be, for example, an all-solid-state lithium metal battery. The all-solid-state lithium metal battery will be described below.

The all-solid-state lithium metal battery includes a negative electrode having a negative electrode current collector and a lithium metal layer, a positive electrode having a positive electrode current collector and a positive electrode mixture layer, and a solid electrolyte layer.

The negative electrode current collector is not particularly limited, but may be, for example, copper foil.

The positive electrode mixture layer includes a positive electrode active material, and may further include a solid electrolyte, a conductive additive, a binder, etc. The positive electrode active material is not particularly limited as long it is capable of absorbing and releasing lithium ions, but may be, for example, a lithium nickel cobalt manganese composite oxide. The solid electrolyte is not particularly limited if it has lithium ion conductivity, but may be, for example, an oxide-based electrolyte or a sulfide-based electrolyte. The conductive additive is not particularly limited if it has electronic conductivity, but may be, for example, carbon black. The binder is not particularly limited as long it is capable of improving the binding property, but may be, for example, styrene butadiene rubber.

The positive electrode current collector is not particularly limited, but may be, for example, aluminum foil.

The solid electrolyte layer includes a solid electrolyte, and may further include a binder, etc. The solid electrolyte is not particularly limited if it has lithium ion conductivity, but may be, for example, an inorganic solid electrolyte such as an oxide-based electrolyte or a sulfide-based electrolyte. The binder is not particularly limited as long it is capable of improving the binding property, but may be, for example, styrene butadiene rubber.

An intermediate layer having a function of uniformly precipitating lithium metal may be formed between the negative electrode and the solid electrolyte layer. This stabilizes the interface between the intermediate layer and the solid electrolyte layer. In this case, the all-solid-state lithium metal battery may be an anode-free battery in which the lithium metal layer is not formed at the time of the first charge. In the anode-free battery, the lithium metal layer is formed after the first charge and discharge.

The intermediate layer contains a metal that can be alloyed with lithium and an amorphous carbon, and may further contain a binder, etc. The metal that can be alloyed with lithium and the amorphous carbon are preferably in nanoparticles. Examples of metals that can be alloyed with lithium include tin (Sn), silicon (Si), zinc (Zn), magnesium (Mg), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), and antimony (Sb). Examples of amorphous carbon include carbon blacks such as acetylene black, furnace black, and ketjen black, coke, and activated carbon. The amorphous carbon may be graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), CNT (carbon nanotube), fullerene, or graphene. The binder is not particularly limited as long it can improve the binding property, but may be, for example, polyvinylidene fluoride (PVDF).